gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

OPTIS2: a new treatment facility at PSI 25 years after introducing ocular proton therapy in Europe – project challenges and comparison with OPTIS

Meeting Abstract

  • J. Verwey - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • J. Heufelder - Berlinprotonen am Helmholtz-Zentrum, Charité - Universitätsmedizin Berlin, Berlin, Germany
  • F. Assenmacher - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • M.-J. van Goethem - UMCG, Groningen, The Netherlands
  • A. Tourovsky - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • M. Grossmann - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • A. Lomax - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • G. Goitein - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • M. Jermann - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland
  • L. Zografos - l'Hopital opthalmique Jules-Gonin, Lausanne, Switzerland
  • E. Hug - Center for Proton Therapy, Paul Scherrer Institut, Villigen PSI, Switzerland

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog217

DOI: 10.3205/09ptcog217, URN: urn:nbn:de:0183-09ptcog2170

Veröffentlicht: 24. September 2009

© 2009 Verwey et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Background: In 1984 PSI started the ocular proton therapy program called OPTIS. To date more than 5200 eye tumours have been treated using a 72 MeV Philips cyclotron. Cyclotron reliability and maintenance issues led to the start of the PROSCAN project in 2000, resulting in the 250 MeV COMET cyclotron to provide both the Gantry 1, Gantry 2 and OPTIS2 treatment rooms with protons. The aims of OPTIS2 are to continue to offer ocular proton therapy at PSI without interruption in a technically modern, patient-friendly environment, maintaining for as far as possible the beam parameters of OPTIS in order to match its clinical success. Demands on beam time are to be minimised to optimise the use of beam time in a multi-room facility.

Materials and methods: The project's main technical challenge concerned beam intensity. Degrading 250 MeV protons to 70 MeV more than 99.5% of the protons are lost. In order to cap treatment duration at one minute, a dramatically more efficient beam shaping system as used in OPTIS had to be designed. Instead of a single scatterer a double scattering (DS) system with multiple-ring scatter foils was opted for. Using DS rather than single scattering affected beam characteristics that required nozzle design changes.

Technical innovations instigated at the Helmholtz-Zentrum, Berlin (Germany) and Institut Curie, Orsay (France) were adapted and incorporated. Architects were invited to design the treatment room.

The nozzle and the control system were to be designed to no longer require daily pre-treatment verification measurements to be able to start patient treatment when beam becomes available.

Results: While the dose rate of OPTIS remains superior to that of OPTIS2, OPTIS2 achieved a transmission increase of up to a factor eight. Distal dose fall-off increased marginally in OPTIS2, but the clinically more relevant lateral penumbra was kept the same. Beam flatness and symmetry were significantly improved in OPTIS2.

OPTIS2 is fitted with computer aided positioning, digital imaging and a robotic chair. A flexible multi-group lighting concept and abundant use of natural materials have introduced a patient friendly atmosphere.

A strict separation of the control system into a Therapy Delivery System and a Therapy Verification System allows for the safe treatment of patients without the need for pre-treatment measurements.

Conclusion: The OPTIS2 project has been a complex project, requiring a completely new nozzle and control system design to cap treatment duration while allowing patient treatments to take place without the need for daily verification measurements. Although the incorporation of the various technological innovations as well as the integration of the facility within an operational clinical environment proved to be challenging, all project aims were met. OPTIS2 ensures that ocular proton therapy remains an important facet of PSI's proton project. OPTIS2 was successfully audited by the Swiss Federal Organisation for Public Health in June, 2009.